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460
Democritus
Democritus began with stating a notion of space that served as its premise. Rather than an attribute of matter that describes its extension, Democritus characterizes space as a receptacle for stationary and moving objects -
Dalton
Atomic theory was all matter was composed of small indivisible particles termed atoms, (2) atoms of a given element possess unique characteristics and weight, and (3) three types of atoms exist: simple (elements), compound (simple molecules), and complex (complex molecules). -
Dimitri Mendeleev
He arranged the periodic table of elements by their atomic weights and if there were any gaps in the table he would let those be filled when the new elements are discovered. -
JJ Thomson
In 1897 the British physicist Joseph John (J. J.) Thomson (1856–1940) discovered the electron in a series of experiments designed to study the nature of electric discharge in a high-vacuum cathode-ray tube -
John Newlands
in 1865 he published his “law of octaves” which states that “any given element will exhibit analogues behaviour to the eighth element following it in the table". -
Rutherford
He developed Bacquerel’s discovery of radioactivity into an exact and documented proof that the atoms of the heavier elements.
Also discovered the half-life of radioactive elements.
Rutherford discovered the Proton. -
Niels Bohr
He discovered electrons moved in a fixed orbit around the nucleus and explained how they emit and absorb energy.
He won the Nobel prize in 1922 for physics. -
James Chadwick
Discovered the neutron and this discovery was crucial to the fission of uranium 235
neutrons do not need to overcome any Coulomb barrier and can therefore penetrate and split the nuclei of even the heaviest elements. -
Aristotle
Aristotle had a method of investigation, defining the subject matter considering the difficulties involved by reviewing the generally accepted views on the subject, and suggestions of earlier writers presenting his own arguments and solutions. -
Period: to
years of chemists